Lithium ion batteries (hereinafter referred as “LIB”) have become one of the most promising secondary batteries in application and development, due to their advantages of higher voltage, higher energy density and long cycle life-span etc. However, along with the continuous development of intellectualization, miniaturization, longer standby time and longer battery life-span of portable electronic apparatuses, and the popularity of higher power and higher energy devices such as electric vehicles, there are increasing requirements on energy density for LIB. For the anode plate, some lithium is always consumed due to the formation of solid electrolyte interface (SEI) film during the initial charging. This causes lithium loss in cathode material, and results in decreased battery capacity and initial coulombic efficiency. This phenomenon is particularly apparent with anodes utilizing silicon-based or tin-based materials (such as silicon alloy and tin alloy) as their active materials.
One common method to increase initial coulombic efficiency is to supplement the anode with lithium. Some researchers have added lithium powder into the anode slurry to do that, and conventionally, polyvinyldiene fluoride (PVDF) is usually used as binder of anode slurry. The disadvantage of PVDF is that before being used as a binder, it must be dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP) However, dissolving PVDF requires large amount of solvent and the solvent is difficult to recycle, which greatly increases production costs. Also, NMP is toxic and can be harmful to technicians. Moreover, lithium powder is light enough to easily float on the surface of the slurry, which makes it difficult to mix uniformly with ordinary solvents and to coat evenly on the current collector. Chinese patent application No. CN1177417A discloses a method to produce lithium-rich LIB, which comprises the following steps: covering an anode surface with a lithium plate, coiling the lithium plate to form battery cells, and then injecting electrolyte to get a lithium-rich LIB. In that conventional method, since conventionally used process to prepare such thin lithium plate in this case is not available, the amount of lithium absorbed by the anode is far less than that provided by the lithium plate. All these will lead to excess supplement of lithium, lithium precipitation in the battery and poor cycle performance etc.